[instarx]

I can easily see the skirts contributing to this. In a normal trailer air flowing under it relieves the low pressure area on the downwind side. The lack of air flowing under this trailer would have increased the negative pressure on the downwind side considerably.

Although I grew up around trucks I'm far from an expert, but I don't think I would put a tractor under it as first choice. I'd think moving the trailer closer to a structure or parking it along those trees in the background would be a better (and safer) solution.

But this raises an interesting question. Since it is pretty common for trailers to blow over while being pulled in high winds I'm wondering if that might be an increased danger for aero trailers on the road. In any event, it is something to think about when this one starts getting used. You seem to have years of experience modifying trailers - have you heard of aero trailers being more tippy in high winds?

Beautiful job on that trailer by the way!